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Principal component analysis of International Ultraviolet Explorer galaxy spectra
We analyse the UV spectral energy distribution of a sample of normalgalaxies listed in the International Ultraviolet Explorer (IUE) NewlyExtracted Spectra (INES) Guide No. 2 - Normal Galaxies using a principalcomponent analysis. The sample consists of the IUE short-wavelength (SW)spectra of the central regions of 118 galaxies, where the IUE apertureincluded more than 1 per cent of the galaxy size. The principalcomponents are associated with the main components observed in theultraviolet (UV) spectra of galaxies. The first component, accountingfor the largest source of diversity, may be associated with the UVcontinuum emission. The second component represents the UV contributionof an underlying evolved stellar population. The third component issensitive to the amount of activity in the central regions of galaxiesand measures the strength of star-formation events.In all the samples analysed here, the principal component representativeof star-forming activity accounts for a significant percentage of thevariance. The fractional contribution to the spectral energydistribution (SED) by the evolved stars and by the young population aresimilar.Projecting the SEDs on to their eigenspectra, we find that none of thecoefficients of the principal components can outline an internalcorrelation or can correlate with the optical morphological types. In asubsample of 43 galaxies, consisting of almost only compact and BCDgalaxies, the third principal component defines a sequence related tothe degree of starburst activity of the galaxy.
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| Starbursts in barred spiral galaxies. VI. HI observations and the K-band Tully-Fisher relation
This paper reports a study of the effect of a bar on the neutralhydrogen (HI) content of starburst and Seyfert galaxies. We also makecomparisons with a sample of ``normal'' galaxies and investigate howwell starburst and Seyfert galaxies follow the fundamental scalingTully-Fisher (TF) relation defined for normal galaxies. 111 Markarian(Mrk) IRAS galaxies were observed with the Nançay radiotelescope,and HI data were obtained for 80 galaxies, of which 64 are newdetections. We determined the (20 and 50%) linewidths, the maximumvelocity of rotation and total HI flux for each galaxy. Thesemeasurements are complemented by data from the literature to form asample of Mrk IRAS (74% starburst, 23% Seyfert and 3% unknown) galaxiescontaining 105 unbarred and 113 barred ones. Barred galaxies have lowertotal and bias-corrected HI masses than unbarred galaxies, and this istrue for both Mrk IRAS and normal galaxies. This robust result suggeststhat bars funnel the HI gas toward the center of the galaxy where itbecomes molecular before forming new stars. The Mrk IRAS galaxies havehigher bias-corrected HI masses than normal galaxies. They also showsignificant departures from the TF relation, both in the B and K bands.The most deviant points from the TF relation tend to have a strongfar-infrared luminosity and a low oxygen abundance. These resultssuggest that a fraction of our Mrk IRAS galaxies are still in theprocess of formation, and that their neutral HI gas, partly of externalorigin, has not yet reached a stationary state.Based on observations obtained at the large radiotelescope ofObservatoire de Nançay, operated by Observatoire de Paris.Tables 5 and 6 are only (and Table 4 also) available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/515
| The evolution of stars and gas in starburst galaxies
In systems undergoing starbursts the evolution of the young stellarpopulation is expected to drive changes in the emission-line properties.This evolution is usually studied theoretically, with a combination ofevolutionary synthesis models for the spectral energy distribution ofstarbursts and photoionization calculations. In this paper we present amore empirical approach to this issue. We apply empirical populationsynthesis techniques to samples of starburst and HII galaxies in orderto measure their evolutionary state and correlate the results with theiremission-line properties. A couple of useful tools are introduced thatgreatly facilitate the interpretation of the synthesis: (1) anevolutionary diagram, the axes of which are the strengths of the young,intermediate age and old components of the stellar population mix; and(2) the mean age of stars associated with the starburst, . These toolsare tested with grids of theoretical galaxy spectra and found to workvery well even when only a small number of observed properties(absorption-line equivalent widths and continuum colours) is used in thesynthesis.Starburst nuclei and HII galaxies are found to lie on a well-definedsequence in the evolutionary diagram. Using the empirically defined meanstarburst age in conjunction with emission-line data, we have verifiedthat the equivalent widths of Hβ and [OIII] decrease for increasing. The same evolutionary trend was identified for line ratios indicativeof the gas excitation, although no clear trend was identified formetal-rich systems. All these results are in excellent agreement withlong-known, but little tested, theoretical expectations.
| The PDS versus Markarian starburst galaxies: comparing strong and weak IRAS emitter at 12 and 25 μm in the nearby Universe
The characteristics of the starburst galaxies from the Pico dos Diassurvey (PDS) are compared with those of the nearby ultraviolet (UV)bright Markarian starburst galaxies, having the same limit in redshift(vh < 7500 km s-1) and absolute B magnitude(MB < -18). An important difference is found: theMarkarian galaxies are generally undetected at 12 and 25 μm in IRAS.This is consistent with the UV excess shown by these galaxies andsuggests that the youngest star-forming regions dominating thesegalaxies are relatively free of dust.The far-infrared selection criteria for the PDS are shown to introduce astrong bias towards massive (luminous) and large size late-type spiralgalaxies. This is contrary to the Markarian galaxies, which are found tobe remarkably rich in smaller size early-type galaxies. These resultssuggest that only late-type spirals with a large and massive disc arestrong emitters at 12 and 25 μm in IRAS in the nearby Universe.The Markarian and PDS starburst galaxies are shown to share the sameenvironment. This rules out an explanation of the differences observedin terms of external parameters. These differences may be explained byassuming two different levels of evolution, the Markarian being lessevolved than the PDS galaxies. This interpretation is fully consistentwith the disc formation hypothesis proposed by Coziol et al. to explainthe special properties of the Markarian SBNG.
| Evolutionary spectral energy distribution diagnostics of starburst galaxies: signature of bimodality
We construct an evolutionary spectral energy distribution (SED) model ofa starburst region, from the ultraviolet to submillimetre wavelengths.This model allows us to derive the star formation rate, optical depth bydust and apparent effective radius of starburst regions at variouswavelengths; as a result, the intrinsic surface brightness of starburstregions can be derived. Using this SED model, we analyse 16ultraviolet-selected starburst galaxies and 10 ultraluminous infraredgalaxies. The derived star formation rates and optical depths arecompared with emission-line measurements and are found to be consistent.The derived apparent effective radii are also consistent withobservations. From the SED analysis, we find a bimodal property of thestar formation rate with the optical depth and the compactness ofstellar distributions. While mild starbursts have a limiting intrinsicsurface brightnessLbolr-2e~= 1012Lsolar kpc-2, intense starbursts tend to be moreheavily obscured and concentrated within a characteristic scale ofre~= 0.3 kpc. We suggest that the mild starbursts can betriggered by a self-gravitating disc instability in which feedback iseffective in the shallow gravitational potential. On the other hand, theintense starbursts can be induced via an external dynamical perturbationsuch as galaxy merging, in which feedback is less effective owing to thedeep gravitational potential attained by the large gas concentrationwithin the central starburst region.
| Star formation rate in galaxies from UV, IR, and Hα estimators
Infrared (IR) luminosity of galaxies originating from dust thermalemission can be used as an indicator of the star formation rate (SFR).Inoue et al. (\cite{inoue00}, IHK) have derived a formula for theconversion from dust IR luminosity to SFR by using the following threequantities: the fraction of Lyman continuum luminosity absorbed by gas(f), the fraction of UV luminosity absorbed by dust (epsilon ), and thefraction of dust heating from old (ga 108 yr) stellarpopulations (eta ). We develop a method to estimate those threequantities based on the idea that the various way of SFR estimates fromultraviolet (UV) luminosity (2000 Å luminosity), Hαluminosity, and dust IR luminosity should return the same SFR. Afterapplying our method to samples of galaxies, the following results areobtained in our framework. First, our method is applied to a sample ofstar-forming galaxies, finding that f ~ 0.6, epsilon ~ 0.5, and eta ~0.4 as representative values. Next, we apply the method to a starburstsample, which shows larger extinction than the star-forming galaxysample. With the aid of f, epsilon , and eta , we are able to estimatereliable SFRs from UV and/or IR luminosities. Moreover, the Hαluminosity, if the Hα extinction is corrected by using the Balmerdecrement, is suitable for a statistical analysis of SFR, because thesame {correction factor for the Lyman continuum extinction (i.e. 1/f)}is applicable to both normal and starburst galaxies over all the rangeof SFR. The metallicity dependence of f and epsilon is also tested:Only the latter proves to have a correlation with metallicity. As anextension of our result, the local (z=0) comoving density of SFR can beestimated with our dust extinction corrections. We show that all UV,Hα , and IR comoving luminosity densities at z=0 give a consistentSFR per comoving volume ( ~ 3x 10-2h M_sun yr-1Mpc-3). Useful formulae for SFR estimate are listed.Tables 1 and 2, and Appendix A are only available in electronic form athttp://www.edpsciences.org
| The WSRT wide-field H I survey. I. The background galaxy sample
We have used the Westerbork array to carry out an unbiased wide-fieldsurvey for H I emission features, achieving an RMS sensitivity of about18 mJy/Beam at a velocity resolution of 17 km s-1 over 1800deg2 and between -1000 < VHel <+6500 kms-1. The primary data consists of auto-correlation spectrawith an effective angular resolution of 49' FWHM, althoughcross-correlation data were also acquired. The survey region is centeredapproximately on the position of Messier 31 and is Nyquist-sampled over60x 30o in RA x Dec. More than 100 distinct features aredetected at high significance in each of the two velocity regimes(negative and positive LGSR velocities). In this paper we present theresults for our H I detections of external galaxies at positive LGSRvelocity. We detect 155 external galaxies in excess of 8sigma inintegrated H I flux density. Plausible optical associations are foundwithin a 30' search radius for all but one of our H I detections in DSSimages, although several are not previously cataloged or do not havepublished red-shift determinations. Our detection without a DSSassociation is at low galactic latitude. Twenty-three of our objects aredetected in H I for the first time. We classify almost half of ourdetections as ``confused'', since one or more companions is catalogedwithin a radius of 30' and a velocity interval of 400 km s-1.We identify a handful of instances of significant positional offsetsexceeding 10 kpc of unconfused optical galaxies with the associated H Icentroid, possibly indicative of severe tidal distortions or uncatalogedgas-rich companions. A possible trend is found for an excess of detectedH I flux in unconfused galaxies within our large survey beam relative tothat detected previously in smaller telescope beams, both as function ofincreasing distance and increasing gas mass. This may be an indicationfor a diffuse gaseous component on 100 kpc scales in the environment ofmassive galaxies or a population of uncataloged low mass companions. Weuse our galaxy sample to estimate the H I mass function from our surveyvolume. Good agreement is found with the HIPASS BGC results, but onlyafter explicit correction for galaxy density variations with distance.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/406/829 and Fig. 3 is onlyavailable in electronic form at http://www.edpsciences.org
| A New Database of Observed Spectral Energy Distributions of Nearby Starburst Galaxies from the Ultraviolet to the Far-Infrared
We present a database of UV-to-FIR data of 83 nearby starburst galaxies.The galaxies are selected based upon the availability of IUE data. Wehave recalibrated the IUE UV spectra for these galaxies by incorporatingthe most recent improvements. For 45 of these galaxies we useobservations by Storchi-Bergmann et al. and McQuade et al. for thespectra in the optical range. The NIR data are from new observationsobtained at the NASA/IRTF and the Mount Laguna Observatory, combinedwith the published results from observations at the Kitt Peak NationalObservatory. In addition, published calibrated ISO data are included toprovide mid-IR flux densities for some of the galaxies. Theoptical-to-IR data are matched as closely as possible to the IUE largeaperture. In conjunction with IRAS and ISO FIR flux densities, all thesedata form a set of observed spectral energy distributions (SEDs) of thenuclear regions of nearby starburst galaxies. The SEDs should be usefulin studying star formation and dust/gas attenuation in galaxies. We alsopresent the magnitudes in the standard BVRI and various HST/WFPC2bandpasses synthesized from the UV and optical wavelength ranges ofthese SEDs. For some of the galaxies, the HST/WFPC2 magnitudessynthesized from the SEDs are checked with those directly measured fromWFPC2 images to test the photometric errors of the optical data andtheir effective matching of apertures with the UV data. The implicationsof the new SEDs on the star formation rates and dust/gas attenuation arebriefly discussed.
| Star formation and dust extinction in nearby star-forming and starburst galaxies
We study the star formation rate and dust extinction properties of asample of nearby star-forming galaxies as derived from Hα and UV (~ 2000 Å) observations and we compare them to those of a sample ofstarburst galaxies. The dust extinction in Hα is estimated fromthe Balmer decrement and the extinction in UV using the FIR to UV fluxratio or the attenuation law for starburst galaxies of Calzetti et al.(\cite{calzetti5}). The Hα and UV emissions are stronglycorrelated with a very low scatter for the star-forming objects and witha much higher scatter for the starburst galaxies. The Hα to UVflux ratio is found to be larger by a factor ~ 2 for the starburstgalaxies. We compare both samples with a purely UV selected sample ofgalaxies and we conclude that the mean Hα and UV properties ofnearby star-forming galaxies are more representative of UV-selectedgalaxies than starburst galaxies. We emphasize that the Hα to UVflux ratio is strongly dependent on the dust extinction: the positivecorrelation found between FHα/FUV andFFIR/FUV vanishes when the Hα and UV fluxare corrected for dust extinction. The Hα to UV flux ratiosconverted into star formation rate and combined with the Balmerdecrement measurements are tentatively used to estimate the dustextinction in UV.
| Strömgren Photometry from z=0 to z~1. I. The Method
We use rest-frame Strömgren photometry to observe clusters ofgalaxies in a self-consistent manner from z=0 to z=0.8. Strömgrenphotometry of galaxies is intended as a compromise between standardbroadband photometry and spectroscopy, in the sense that it is moresensitive to subtle variations in spectral energy distributions than theformer, yet much less time-consuming than the latter. principalcomponent analysis is used to facilitate extraction of information fromthe Strömgren data. By calibrating the principal components usingwell-studied galaxies, as well as models of stellar populations, wedevelop a purely empirical method to detect, and subsequently classify,cluster galaxies at all redshifts smaller than 0.8. Interlopers arediscarded with unprecedented efficiency (up to 100%). The firstprincipal component essentially reproduces the Hubble sequence and canthus be used to determine the global star formation history of clustermembers. The (PC2, PC3) plane allows us to identify Seyfert galaxies(and distinguish them from starbursts) based on photometric colorsalone. In the case of E/S0 galaxies with known redshift, we are able toresolve the age-dust-metallicity degeneracy, albeit at the accuracylimit of our present observations. We use this technique in later papersto probe galaxy clusters well beyond their cores and to faintermagnitudes than spectroscopy can achieve, because the faint end of theluminosity function as well as the outer cluster regions seem to exhibitthe strongest evolutionary trends. We are able to directly compare thesedata over the entire redshift range without a priori assumptions becauseour observations do not require first-order k-corrections. Thecompilation of such data for different cluster types over a wideredshift range is likely to set important constraints on the evolutionof galaxies and on the clustering process.
| Excitation Mechanism of Near-Infrared [Fe II] Emission in Seyfert and Starburst Galaxies
The excitation mechanism of near-infrared [Fe II] emission in Seyfertand starburst galaxies is studied. We carry out numerical calculationsfor photoionization and shock heating, and compare the results with theobservational data. The gas-phase abundance of iron is found to bealways low. This means that destruction of iron-bearing grains isinsufficient to affect the [Fe II] strength. We propose that the [Fe II]strength depends primarily on the ionization structure. The [Fe II]emission is excited by electron collisions in a zone of partiallyionized hydrogen, which is extensive when the gas is heated by X-rays orby a shock. These two processes are discriminated by the electrontemperature of the [Fe II] region: 8000 K in heating by X-rays, and 6000K in shock heating. The [Fe II] emission of a Seyfert galaxy originatesin the narrow-line region, which is heated by X-rays from the nucleusand by shocks due to the nuclear outflow. From the [Fe II] temperature,we propose that the heating by X-rays is more important. On the otherhand, the [Fe II] emission of a starburst galaxy originates in thesupernova-driven shocks. We find that 0.2% of the shock energy istransferred into the [Fe II]a6D9/2-a4D7/2 line at 1.257μm.
| The Arizona-New Mexico Spectroscopic Survey of Galaxies. I. Data for the Western End of the Perseus Supercluster
We present new optical spectroscopic data for 347 galaxies in the regionof the Perseus supercluster. The new data were obtained using theSteward Observatory 2.3 m telescope and cover the whole optical window.Included are redshifts (for 345 objects), absorption-line equivalentwidths, a continuum index measuring the 4000 Å break, andemission-line flux ratios. After 11 objects are rejected for being toofaint and redshifts for 26 objects are added from the literature, wearrive at a complete sample of 361 galaxies. The distribution ofredshifts for the whole sample is examined, and we show the relationshipof the continuum index to morphology.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Age and Dust Degeneracy for Starburst Galaxies Solved?
We present a newly built spectral evolution model of galaxies thatincludes both stellar and dust effects. Applying the model to 22 nearbystarburst galaxies shows that far-infrared (FIR) luminosity of galaxieshelps to break the age-dustiness degeneracy. We have derived a uniquesolution of age and the dustiness for each starburst galaxy. Theresulting starburst ages and optical depths are in the range 10<=t(Myr)<=500 and 0.5<=tau_V<=5.0, respectively. The result isrobust and is almost independent of model assumptions such as dustdistributions, extinction curves, and burst strengths. With the rapidlygrowing sensitivity of submillimeter detectors, it should becomepossible in the near future to determine the age and tau_V ofstar-forming galaxies at redshifts z~=3 and beyond. Accurate estimatesof tau_V for Lyman-break galaxies and high-z galaxies might require asubstantial revision of the previously claimed picture of star formationhistory over the Hubble time.
| Dust Absorption and the Ultraviolet Luminosity Density at Z~3 as Calibrated by Local Starburst Galaxies
We refine a technique to measure the absorption-corrected ultraviolet(UV) luminosity of starburst galaxies using rest-frame UV quantitiesalone and apply it to Lyman-limit U dropouts at z~3 found in the HubbleDeep Field (HDF). The method is based on an observed correlation betweenthe ratio of far-infrared (FIR) to UV fluxes with spectral slope beta (aUV color). A simple fit to this relation allows the UV flux absorbed bydust and reprocessed to the FIR to be calculated, and hence thedust-free UV luminosity to be determined. International UltravioletExplorer spectra and Infrared Astronomical Satellite fluxes of localstarbursts are used to calibrate the F_FIR/F_1600 versus beta relationin terms of A_1600 (the dust absorption at 1600 Å) and thetransformation from broadband photometric color to beta. Bothcalibrations are almost completely independent of theoreticalstellar-population models. We show that the recent marginal andnondetections of HDF U dropouts at radio and submillimeter wavelengthsare consistent with their assumed starburst nature and our calculatedA_1600. This is also true of recent observations of the ratio of opticalemission-line flux to UV flux density in the brightest U dropouts. Thislatter ratio turns out not to be a good indicator of dust extinction. InU dropouts, absolute magnitude M_1600,0 correlates with beta: brightergalaxies are redder, as is observed to be the case for local starburstgalaxies. This suggests that a mass-metallicity relationship is alreadyin place at z~3. The absorption-corrected UV luminosity function of Udropouts extends up to M_1600,0~-24 AB mag, corresponding to a starformation rate ~200 M_solar yr^-1 (H_0=50 km s^-1 Mpc^-3 and q_0=0.5 areassumed throughout). The absorption-corrected UV luminosity density atz~3 is rho_1600,0>=1.4x10^27 ergs^-1 Hz^-1 Mpc^-1. It is still alower limit since completeness corrections have not been done andbecause only galaxies with A_1600<~3.6 mag are blue enough in the UVto be selected as U dropouts. The luminosity-weighted meandust-absorption factor of our sample is 5.4+/-0.9 at 1600 Å.
| Ultraviolet spectral properties of magellanic and non-magellanic irregulars, H BT II and starburst galaxies
This paper presents the results of a stellar population analysisperformed on nearby (V_R<=5 000 km s^{-1}) star-forming galaxies,comprising magellanic and non-magellanic irregulars, H Ii and starburstgalaxies observed with the IUE satellite. Before any comparison ofgalaxy spectra, we have formed subsets according to absolute magnitudeand morphological classification. Subsequently, we have coadded thespectra within each subset into groups of similar spectral properties inthe UV. As a consequence, high signal-to-noise ratio templates have beenobtained, and information on spectral features can now be extracted andanalysed. Seven groups resulted from this procedure: the magellanicirregulars (including H Ii galaxies) produced two different bluespectral groups; the non-magellanic irregulars could be grouped into twospectral groups with rather peculiar properties; and the luminousstarbursts produced one flat and two blue template spectra. Theirstellar populations are analysed by means of a population synthesisalgorithm based on star cluster spectral components. The syntheticspectra reproduce the observed ones successfully (except thenon-magellanic irregular groups) both in terms of continuum distributionand spectral features. The synthesis flux fractions of different agegroups were transformed into mass fractions, allowing inferences on thestar formation histories. Young stellar populations (age <500 Myrs)are the main flux contributors; in a few cases the intermediate agepopulation (age~1 M_B-2 Myrs) is important, while the old bulgepopulation contributes at most with ~2 % of the lambda2646 Angstromsflux in the case of starburst galaxies, and is negligible in themagellanic irregulars. We also study the reddening values and theextinction law: an SMC-like extinction law is appropriate for all cases.Based upon data collected with the International Ultraviolet Explorer(IUE) Satellite, supported by NASA, SERC and ESA.
| The Ultraviolet Spectroscopic Properties of Local Starbursts: Implications at High Redshift
We report the results of a systematic study of the vacuum ultraviolet (lambda ~= 1150-2000 Angstroms) spectra of a sample of 45 starburst andrelated galaxies observed with the IUE satellite. These span broadranges in metallicity (from 0.02 to 3 times solar), bolometricluminosity (~107-4 x 1011 Lȯ), and galaxy properties (e.g.,including low-mass dwarf galaxies, normal disk galaxies, and massivegalactic mergers). The projected size of the IUE spectroscopic apertureis typically 1 to several kpc and therefore usually encompasses theentire starburst and is similar to the aperture sizes used forspectroscopy of high-redshift galaxies. Our principal conclusion is thatlocal starbursts occupy a very small fractional volume in themultidimensional manifold defined by such fundamental parameters as theextinction, metallicity, and vacuum-UV line strengths (both stellar andinterstellar) of the starburst and the rotation speed (mass) andabsolute magnitude of the starburst's "host" galaxy. More metal-richstarbursts are redder and more heavily extinguished in the UV, are moreluminous, have stronger vacuum-UV lines, and occur in more massive andoptically brighter host galaxies. We advocate using these localstarbursts as a "training set" to learn how to interpret the rest frameUV spectra of star-forming galaxies at high redshift better, and westress that the degree of similarity between local starbursts andhigh-redshift galaxies in this multidimensional parameter space canalready be tested empirically. The results on local starbursts suggestthat the high- redshift "Lyman Dropout" galaxies are typically highlyreddened and extinguished by dust (by an average factor of 5-10 in theUV), may have moderately high metallicities (0.1-1 times solar?), areprobably building galaxies with stellar surface-mass densities similarto present-day ellipticals, and may be suffering substantial losses ofmetal-enriched gas that can "pollute" the intergalactic medium.
| Surface Brightness of Starbursts at Low and High Redshifts
Observations in the rest-frame ultraviolet from various space missionsare used to define the nearby starburst regions having the highestsurface brightness on scales of several hundred parsecs. The brightlimit is found to be 6 x 10^-16 ergs cm^-2 s^-1 Å^-1 arcsec^-2 forrest-frame wavelength of 1830 Å. Surface brightness in thebrightest pixel is measured for 18 galaxies in the Hubble Deep Fieldhaving z > 2.2. After correcting for cosmological dimming, we findthat the high-redshift starbursts have intrinsic ultraviolet surfacebrightness that is typically 4 times brighter than low-redshiftstarbursts. It is not possible to conclude whether this difference iscaused by decreased dust obscuration in the high-redshift starburstregions or by intrinsically more intense star formation. Surfacebrightness enhancement of starburst regions may be the primary factorfor explaining the observed increase with redshift of the ultravioletluminosity arising from star formation.
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| A Spectral Study of Clumpy Irregular Galaxies
Not Available
| Search and Redshift Survey for IRAS Galaxies behind the Milky Way and Structure of the Local Void
This is the third and final paper of our systematic visual search forIRAS galaxies behind the Milky Way at |b| <= 15 deg. This paperpresents a catalog of 950 IRAS galaxies with 60 mu m flux densitieslarger than 0.6 Jy located between l = 0 deg and 150 deg, of which 293are newly identified by this search. We made a redshift survey for theidentified galaxies and obtained new redshift data of 171 galaxies. Wealso present newly measured redshifts of 27 IRAS galaxies between l =150 deg and 225 deg at |b| <= 15 deg. In this paper we studied thestructure of the Local void using IRAS galaxies and galaxies from theThird Reference Catalogue of Bright Galaxies in the region l = 30deg--120 deg and b = -50 deg to +30 deg. The center of the Local voidturned out to be located at l ~ 60 deg, b ~ -15 deg, and cz ~ 2500 kms-1, and the size is about 2500 km s-1 along the direction toward thecenter.
| Dust in Starburst Galaxies
To investigate the nature of starburst dust, we constructed a model ofthe stars and dust in starburst galaxies and applied it to 30 observedstarburst spectral energy distributions (SEDs). The starburst model wasconstructed by combining two stellar evolutionary synthesis models witha model describing the radiative transfer of stellar photons throughdust. The stellar evolutionary synthesis models were used to compute thedust-free SEDs for stellar populations with ages between 1 x 106 and 15x 109 yr. Using a Monte Carlo radiative transfer model, the effects ofdust were computed for average Milky Way (MW) and Small Magellanic Cloud(SMC) dust, two different star/dust geometries, and locally homogeneousor clumpy dust. Using color-color plots, the starburst model was used tointerpret the behavior of 30 starbursts with aperture-matched UV andoptical SEDs (and IR for 19 of the 30) from previous studies. From thecolor-color plots, it was evident that the dust in starbursts has anextinction curve lacking a 2175 Angstroms bump, like the SMC curve, anda steep far-UV rise, intermediate between the MW and SMC curves. Thestar/dust geometry that is able to explain the distribution of the 30starbursts in various color-color plots has an inner dust-free sphere ofstars surrounded by an outer star-free shell of clumpy dust. Whencombined with other work from the literature on the Orion region and the30 Dor region of the Large Magellanic Cloud, this work implies a trendin dust properties with star formation intensity.
| The Spectral Energy Distribution of Normal, Starburst, and Active Galaxies.
We present the results of an extensive literature search ofmultiwavelength data for a sample of 59 galaxies, consisting of 26Starbursts, 15 Seyfert 2's, 5 LINER's, 6 normal spirals and 7 normalelliptical galaxies. The data include soft X-ray fluxes, ultraviolet andoptical spectra, near, mid/far infrared photometry and radiomeasurements, selected to match as closely as possible the IUE aperture(10\arcsecx20\arcsec). The galaxies are separated into 6 groups withsimilar characteristics, namely, Ellipticals, Spirals, LINER's, Seyfert2's, Starbursts of Low and High reddening, for which we create averagespectral energy distributions (SED). The individual groups SED's arenormalized to the lambda 7000 Angstroms flux and compared, looking forsimilarities and differences among them. We find that the SED's ofNormal Spirals and Ellipticals are very similar over the entire energyrange, and fainter than those of all other groups. LINER's SED's aresimilar to those of Seyfert 2's and Starbursts only in the visual tonear-IR waveband, being fainter in the remaining wavebands. Seyfert 2'sare similar to Starbursts in the radio to near-IR waveband, fainter inthe visual to ultraviolet, but stronger in the X-rays. Low and Highreddening Starbursts are similar along the entire SED, differing in theultraviolet, where Low reddening Starbursts are stronger, and in themid/far IR where they are fainter. We have also collectedmultiwavelength data for 4 HII regions, a thermal supernova remnant, anda non-thermal supernova remnant (SNR), which are compared with theStarburst SED's. The HII regions and thermal SNR's have similar SED's,differing only in the X-ray and far infrared. The non-thermal SNR SED isa flat continuum, different from all the other SED's. Comparing theSED's of Starbursts and HII regions we find that they are similar in themid/far IR parts of the spectrum, but HII regions are fainter in theradio and X-rays. Starbursts are also stronger than HII regions in thevisual and near-IR parts of the spectrum, due to the contribution fromold stars to Starbursts. The bolometric fluxes of the different types ofgalaxies are calculated integrating their SED's. These values arecompared with individual waveband flux densities, in order to determinethe wavebands which contribute most to the bolometric flux. In Seyfert2's, LINER's and Starbursts, the mid/far IR emission are the mostimportant contributers to the bolometric flux, while in normal Spiralsand Ellipticals this flux is dominated by the near-IR and visualwavebands. Linear regressions were performed between the bolometric andindividual band fluxes for each kind of galaxy. These fits can be usedine the calculation of the bolometric flux for other objects of similaractivity type, but with reduced waveband information.
| Reddening and Star Formation in Starburst Galaxies
The reddening properties and the star formation history of a sample of19 starburst galaxies are investigated using multiwavelengthspectroscopy and infrared broad band photometry. New photometric data inthe J, H, and K bands of the central starburst regions are supplementedwith previously published spectra, covering the wavelength range0.12-2.2 mu m. In the infrared, the reddening value derived for thestellar continuum is in agreement with that of the ionized gas, but thetwo values diverge at shorter wavelengths; in the UV, the mean opticaldepth of the dust in front of the stars is smaller, being only 60%, thanthe optical depth of the dust in front of the nebular gas. Thisdifference can be better understood if the UV-bright stellar populationand the ionized gas are not co-spatial. A model of foreground clumpydust, with different covering factors for the gas and the stars, isproposed to account for the difference in reddening. A ``templatestarburst spectrum'', derived by combining the reddening-corrected UV,optical, and infrared data of all the galaxies in the sample, is used toinvestigate the star formation history of the galaxies. Spectralsynthesis models indicate that the observed UV emission can beattributed to a stellar population which is undergoing active starformation at a constant rate since ~ 2x10(7) yr, in agreement with thesupernova rates derived from the [FeII] emission line in the infrared.At least two, and probably more, intermediate age populations(age<2x10(9) yr) contribute to the optical and infrared emission,while populations older than ~ 2x10(9) yr do not contributesignificantly to the template. The stellar composition of the templatespectrum suggests episodic star formation over the last 10(9) yr, withstar formation rates as large as or larger than the present rates. Thesynthetic stellar populations are generated according to an Initial MassFunction (IMF) with Salpeter slope (alpha =2.35) in the mass range0.1-100 Msun, and reproduce a number of observationalconstraints, such as the spectral energy distribution of the templatespectrum, the equivalent width of the atomic hydrogen emission lines,and the mass-to-light ratios; the data, then, do not provide indicationfor a high-mass-star truncated or a low-mass-star deficient IMF instarburst galaxies.
| Dust Obscuration in Starburst Galaxies from Near-Infrared Spectroscopy
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...458..132C&db_key=AST
| A multifrequency radio continuum and IRAS faint source survey of markarian galaxies
Results are presented from a multifrequency radio continumm survey ofMarkarian galaxies (MRKs) and are supplemented by IRAS infrared datafrom the Faint Source Survey. Radio data are presented for 899 MRKsobserved at nu = 4.755 GHz with the National Radio Astronomy Observatory(NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% ofthose objects in Markarian lists VI-XIV. In addition, 1.415 GHzmeasurements of 258 MRKs, over 30% of the MRKs accessible from theNational Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported.Radio continuum observations of smaller numbers of MRKs were made at10.63 GHz and at 23.1 GHz and are also presented. Infrared data from theIRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, withreasonably secure identifications extracted from the NASA/IPACExtragalactic Database. MRKs exhibit the same canonical infraredcharacteristics as those reported for various other galaxy samples, thatis well-known enhancement of the 25 micrometer/60 micrometer color ratioamong Seyfert MRKs, and a clear tendency for MRKs with warmer 60micrometer/100 micrometer colors to also possess cooler 12 micrometer/25micrometer colors. In addition, non-Seyfert are found to obey thewell-documented infrared/radio luminosity correlation, with the tightestcorrelation seen for starburst MRKs.
| Ultraviolet to optical spectral distributions of northern star-forming galaxies
We report spectral energy distribution from the UV to the optical for asample of 31 northern star-forming galaxies. We also presentmeasurements for emission-line fluxes, continuum levels, and equivalentwidths of absorption features for each individual spectrum as well asaverages for the eight galactic activity classes, including normal,starburst, Seyfert 2, blue compact dwarf, blue compact, Low-InonizationNuclear Emission Regions (LINER), H II, and combination LINER-H IIgalaxies.
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